Well drilling master bushing assemblies



Sept. 18, 1956 w. A. ABEGG 2,763,468

WELL DRILLING MASTER BUSHING ASSEMBLIES Filed July 24, 1953 -%"j6 W24 TEA? A ABEGG,

16 I! 53 .INVENTOR.

United States Patent WELL DRILLING MASTER BUSHING ASSEMBLIES Walter A. Abegg, Los Angeles, Calif., assignor to Abegg & Reinhold C0., Los Angeles, Calif., a corporation of California Application July 24, 1953, Serial No. 371,857

7 Claims. (Cl. 255-23) This invention relates to improved master bushing assemblies for use in well drilling rotary tables, to serve the dual purposes of transmitting rotary movement from the table to a kelly bushing, and receiving slips to support a pipe string in the table.

The conventional master bushing for a rotary table includes a plurality of interconnected segments forming a vertical opening having an upper square portion for receiving a kelly bushing, and a lower tapering portion for receiving pipe supporting slips. The bushing is formed segmentally to permit its removal laterally from about a drill pipe in order that a bit or other enlargement may pass upwardly through the table.

This conventional type of master bushing has had several distinct disadvantages in use. In the first place, because of the segmental formation of the bushing, the lateral forces exerted by the pipe supporting slips in use act to urge the bushing segments relatively apart and against the rotary table, in a manner enlarging the square recess in the table, and eventually distorting the recess to anunusable condition. This table damage is encountered increasingly more frequently as wells are drilled to greater and greater depths. Further, after a rotary table has become worn and its central opening somewhat enlarged, the two or more bushing sections tend to move farther apart when in use, to an extent such that they no longer form a true circular slip receiving opening. As a result, the slips are not properly positioned by the bowl section-s, and being improperly positioned are subject to excessive wear, deformation and sometimes breakage. Further, the improper positioning of the slips may deform and locally weaken the engaged pipe in a manner rendering it susceptible to failure in the well.

The general object of the present invention is to provide an improved bushing assembly which is adapted to overcome the above disadvantages of conventional structures, and specifically to prevent the transmission of radially outward or spreading forces from the pipe engaging slips through the master bushing to the rotary table. Further, the bushing is designed to attain this result while at the same time serving effectively its two kelly driving and slip supporting functions, and yet being adapted for easy conversion to a condition for passing through the bushing a large diameter object such as a drill bit when necessary.

To achieve the above purposes, I employ a bushing assembly comprising a rigid essentially annular one piece shell or body receivable within the rotary table and contaming an opening through which a drill pipe or other pipe string may extend. An upper portion of this opening has a non-circular configuration, conventionally square, to receive and drive the correspondingly non-circular portion of a kelly bushing. The lower portion of the opening, on the other hand, is adapted to receive and support a plurality of bowl segments which form together a tapered recess for receiving the usual pipe supporting slips. Of particular importance is the formation of the bowl segments in a manner such that the upper noncircular portion of the opening in the bushing body is accessible and adapted to drive a kelly bushing even when the bowl segments are positioned in the body. At the same time, however, the bowl segments may be easily removable from the body to increase the effective size of its opening when it is desired to move a bit or other large object through the bushing unit.

An additional feature of the invention involves the formation in the bowl and each of the shell segments of a horizontally extending opening for receiving a hook or other tool by which the part is removable from the rotary table.

The above and other features and objects of the present invention will be better understood from the following detailed description of the typical embodiment illus trated in the accompanying drawing, in which:

Fig. 1 is a perspective view of a well drilling rotary table containing a bushing assembly constructed in accordance with the present invention;

Fig. 2 is an enlarged plan view of the bushing assembly;

Fig. 3 is a vertical section taken on line 3-3 of Fig. 2; and

Figs. 4 and 5 are enlarged fragmentary vertical sections taken on lines 4-4 and 5-5 respectively of Fig. 2.

The apparatus shown in Fig. 1 includes a conventional rotary table 10 mounted on a base 11 for rotation about a vertical axis and driven by the usual drive shaft 12. The rotary table 10 contains a central vertically extending opening 13 within which is mounted the bushing assembly 14 of the present invention.

As best seen in Figs. 2 and 3, the bushing assembly includes a rigid one piece metal shell or body 15, and a pair of complementary semi-circular bowl segments 16 received within body 15. The body has an upper externally substantially square portion 17 received within a correspondingly shaped upper portion 18 of the rotary table opening to be positively driven by the table. He neath its upper square portion 17, body 15 has a lower externally cylindrical and reduced portion 19 received within cylindrical portionZtl of the rotary table opening.

At its inside, body 15 has a vertically extending opening or passage 113 which receives bowl segments 16, and which is defined in part by a lower cylindrical inner surface 21, and an upper enlarged diameter cylindrical surface 22. Between these two cylindrical surfaces, the bushing body forms an annular horizontal bowl supporting seat 23. Within the upper externally square portion 17 of the bushing body, and above bowl segments 16, opening 113 in body 15 has an upper non-circular portion, which is preferably essentially square and is formed by providing four evenly circularly spaced corner recesses 24 in the body, extending horizontally outwardly beyond the diameter of cylindrical surface 22. The exact corners 25 of recesses 24 may be cut away or relieved cylindrically as shown, and the lower portions of the recess walls may be undercut at 26. Circularly between corner recesses 24, there are four arcuate partial cylindrical surfaces 22a (see Fig. 2) which may be considered as upper continuations or portions of surface 22 and which allow bowl segments 16 to he slipped downwardly through the upper noncircular portion of opening 113 into the lower circular portion of that opening. As will be understood, the upper non-circular essentially square portion of body opening 113, formed by corner recesses 24 and surfaces 22a is provided for reception of the square portion of a conventional kelly driving bushing (not shown), and is adapted to receive the kelly bushing even when the bowl segments 16 are in place within the body. When the square portion of a kelly bushing is thus received Within the upper noncircular portion of body opening 113, with the corners of the kelly bushing received within corner recesses 24, the body is effective to rotatively drive the kelly bushing.

The two bowl segments 16 abut at 27 and 28 to form I together a circular slip receiving bowl structure. Externally, the bowl segments have upper and lower semi-cylindrical surfaces 29 and 30 engaging body surfaces 22 and 21 respectively. Between surfaces..29 and'30, the'bowl. segments have semi-circular downwardly facing horizontal shoulders 31 engageable with seat 23 on the bushing body to support the segments in the body.

At their inside, segments 16 form together a downwardly tapering bowl surface 32, for engaging the correspondingly tapered outer surfaces 33 of the usual pipe gripping slips 34. Each of the bowl segments contains at a central location, an opening 35 (see Fig. 4) to receive a hook 36 for removing the segments upwardly from the bushing body and rotary table. Body 15 may contain two similar hook receiving openings 37 at diametrically opposite corners of its upper square portion, to facilitate removal of the body from the rotary table (see Figs. 2 and 5).

In use, bushing body 15 is first inserted into opening 13 in the rotary table, and bowl segments 16 are then placed in the bushing body as shown. When it is desired to support a pipe string 38 in the table, slips 34 are placed within the tapered opening formed by the bowl segments to grip and support the pipe. As will be appreciated, the weight of pipe 38 tends to urge the pipe and slips downwardly, with the result that bowl surface 32 wedges the slips tightly inwardly against the pipe. During actual drilling, the slips 34 are removed from the master bushing assembly, and a kelly bushing is placed in position, with its upper square portion received and supported in the upper square portion of bushing opening 113. The kelly bushing may rest on either the upper edge surfaces of the bowl segments 16, or the upwardly facing surfaces in the corners 24 of the upper non-circular portion of body opening 113. When it is desired to pass a bit or other enlargement upwardly through the table, segments 16 may be very easily removed from the bushing body, to present an enlarged opening within the bushing assembly.

Because of the rigid one piece formation of bushing body 15, this body serves at all times to maintain bowl segments 16 against relative separation. Consequently, separating forces exerted by slips 34 against bowl segments 16 are not transmitted to the rotary table, but instead are taken by body 15, so that the table is not excessively worn or distorted, even under heavy loads. Further, the inner slip engaging surface 32 formed by the bowl segments is maintained exactly circular to properly engage and position the various slips. Such accurate positioning of the slips prevents their deformation, excessive wear, or breakage, and also prevents the pipe deformation which sometimes results from improper vslip positioning. Further, the accurate relative positioning of bowl segments 16 is maintained even though the rotary table may become worn about opening 13.

I claim:

1. A well-drilling master bushing assembly comprising an outer rigid body adapted to be received and supported in a rotary table recess and containing an opening extending vertically therethrough, said body having an upper externally non-circular portion to be received and supported in and .rotatably driven by an upper non-circular portion of said rotary table recess, said body having a lower portion of externally reduced dimension extending downwardly into a lower portion of said rotary table recess, said upper non-circular portion of the body extending laterally beyond said lower portion, and a plurality of slip bowl segments supported in a lower portion of said body opening and having downwardly converging inner slip engaging surfaces, means for supporting said slip bowl segments in said body, said outer body comprising a one-piece rigid member the material of which extends entirely about said opening continuously and without interruption vso that lateral expanding forces exerted against the body are taken directly by it without transmission to the rotary table, said slip bowl segments being completely removable from said outer body to pass a drill bit through the body, the material of said body forming a non-circular upper portion of said opening adapted to receive and directly engage and rotatably drive a mating non-circular portion of a kelly bushing, and said slip bowl segments being positioned low enough in the body to allow reception of said non-circular portion of the kelly bushing in said upper non-circular portion of the body opening in direct rotary driving engagement with the body at that location without removal of the slip bowl segments from the body.

2. A well drilling master bushing assembly as recited in claim 1, in which said means for supporting the .slip bowl segments comprise shoulders on the body and segments interengaging to support the segments in the body.

3. A well drilling master bushing assembly as recited in claim 1, in which said lower portion of the body is externally cylindrical.

4. A well drilling master bushing assembly as recited in claim 1, in which said body and segments have engaging vertically extending cylindrical surfaces.

5. A well drilling master bushing assembly as recited in claim 1, in which said upper portion of the body is externally essentially square, and said upper portion of the body opening is essentially square.

6. A well drilling master bushing assembly as recited in claim 5, in which said bowl segments are arcuate, said bowl segment supporting means comprising arcuate shoulders on the segments and body engageable beneath said upper essentially square portion of the body opening to support the segments in the body, andlsaid segments and body having engaging cylindrical surfaces both above and beneath said shoulders.

7. A well drilling master bushing assembly as recited in claim 1, in which said body opening has a lower essentially circular portion beneath and of a smaller horizontal dimension than said upper non-circular portion thereof and within which said slip bowl segments are received.

References Cited in the file of this patent UNITED STATES PATENTS 2,182,935 Whann Dec. l2, 1939 2,533,597 Maier Dec. 12, 1950 2,575,831 Pearce Nov. 20, 1951 

